Engine cooling fans with uneven blade spacing

ABSTRACT

Methods and systems are provided for a fan. In one example, a fan may include a plurality of blades separated by spacings. The spacing is one of a small blade spacing, a medium blade spacing, and a large blade spacing. The size as well as the arrangement of the small, medium, and the large blade spacings are determined by minimizing an imbalance force and pressure generated by the fan at a plurality of frequencies.

FIELD

The present description relates generally to methods and systems of afan with uneven blade spacing.

BACKGROUND/SUMMARY

Engine cooling fans may cause noise, vibration, and harshness (NVH) dueto their large size, high power, and excessive engagement during vehicleoperation. Rotation of the cooling fan may generate tonal noise andvibrations at various frequencies including a fundamental frequency (ora first order imbalance) and harmonic frequencies.

One approach to address the NVH issue include arranging the fan bladeswith non-uniform spacing. One example approach is shown by Delvaux, etal. in U.S. Pat. No. 8,678,752. Therein, fan blades are separated withspacers of different sizes. The spacers may be arranged in a variety ofrepeating patterns, or in a random order.

However, the inventors herein have recognized potential issues with suchsystems. As one example, though non-uniform spacing may change thefrequency distribution of NVH by spreading the harmonics over a widerfrequency range, the asymmetric blade arrangement may increase NVH dueto an increased imbalance force. The imbalance force may generate boomnoise and vibrations at the seat track and the steering wheel.Additionally, the size and the arrangement of the spacers may affect thefrequency distribution of NVH and the imbalance force. The search forthe spacer arrangement with minimal imbalance force and preferredfrequency distribution may be difficult due to the large number ofpossible spacer arrangements. The possible combinations of spacerarrangements may increase exponentially with the number of the fanblades. As one example, a fan with n blades and spacers of r sizes mayhave n!/(n-r)! possible combinations of spacer arrangement. As anotherexample, if the fan has six blades and spacers of three sizes, there areover 13 million unique combinations of spacer arrangements. If the fanhas seven blades and spacers of three sizes, there are over 580 millionunique combinations of spacer arrangements.

In one example, the issues described above may be addressed by a fanincluding blades disposed circumferentially around a hub. The adjacentblades may be separated by the spacing selected from one of a smallblade spacing S, a medium blade spacing M, and a large blade spacing L.In one embodiment, the fan may include six blades. The fan may includetwo small blade spacings, two medium blade spacings, and two large bladespacings, wherein the medium blade spacing is smaller than the largeblade spacing and larger than the small blade spacing. In anotherembodiment, the fan may include seven blades. The fan may include onemedium blade spacing, at least two small blade spacings adjacent to eachother, and at least two large blade spacings. In another embodiment, thefan may include eight blades. The fan may include a plurality of smallblade spacings and a plurality of large blade spacings arranged in thesequence of LLSSL. In yet another embodiment, the fan may include nineblades. The fan may include a plurality of small blade spacings and aplurality of large blade spacings arranged in a sequence of LLSS. Inthis way, NVH from fan with uneven blade spacing may be minimized.

As one example, the fan may be designed with uneven spacing betweenadjacent blades. The spacing may be selected among a small bladespacing, a medium blade spacing, and a large blade spacing. The size ofthe small, medium, and large blade spacings, as well as the sequence ofarrangement of the blade spacings circumferentially relative to the hubof the fan, may be determined through an optimization process thatrecognizes only certain harmonics should be minimized. Further, theoptimization process minimizes the imbalance force that caused by unevenblade spacing. During optimization, a frequency distribution of pressuregenerated by a rotating fan, as well as the imbalance force, arecalculated. The optimal size and arrangement of the blade spacings maybe determined by minimizing the magnitude of the imbalance force and themagnitude of the pressure at one or more selected harmonic frequencies,while ignoring other frequencies and harmonics. By analyzing thepressure at selected frequencies, the computation burden is reduced.Further, NVH generated at the objectionable harmonics as well as theimbalance force may be significantly reduced in a vehicle applicationdue to the fact that certain frequencies contribute more to customerannoyance than others depending on the relative magnitudes of theharmonics.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a cooling system in a motor vehicle.

FIG. 2 is an example method for determining the arrangement of blades ofa fan.

FIG. 3 illustrates example results of an optimization process for asix-blade fan.

FIG. 4A shows one example of a fan with six blades.

FIG. 4B shows another example of a fan with six blades.

FIG. 5A shows one example of a fan with seven blades.

FIG. 5B shows another example of a fan with seven blades.

FIG. 6A shows one example of a fan with eight blades.

FIG. 6B shows another example of a fan with eight blades.

FIG. 7A shows one example of a fan with nine blades.

FIG. 7B shows another example of a fan with nine blades.

FIG. 7C shows another example of a fan with nine blades.

DETAILED DESCRIPTION

The following description relates to systems and methods for a fan withuneven spacing between adjacent blades. For example, the fan may be acooling fan of a cooling system coupled to a vehicle, as shown inFIG. 1. The spacings between blades may be selected from the small,medium, and large blade spacings. The size of each blade spacing and thearrangement of these blade spacings around the hub may be determinedthrough an optimization process shown in FIG. 2. The optimizationprocess minimizes the imbalance force and pressure generated by the fanat various frequencies. FIG. 3 shows example results of the optimizationprocess for a six-blade fan. Structure of fan with optimized bladearrangement is shown in FIGS. 4A-4B, 5A-5B, 6A-6B, and 7A-7C. FIGS.4A-4B shows two examples of six-blade fans. FIGS. 5A-5B shows twoexamples of seven-blade fans. FIGS. 6A-6B shows two examples ofeight-blade fans. FIGS. 7A-4C shows three examples of nine-blade fans.

FIG. 1 is a schematic depiction of an example embodiment of vehiclecooling system 100 in vehicle 102. Vehicle 102 has drive wheels 106, apassenger compartment 104, and an under-hood compartment 103. Under-hoodcompartment 103 may house various under-hood components under the hood(not shown) of motor vehicle 102. For example, under-hood compartment103 may house internal combustion engine 10. Internal combustion engine10 has a combustion chamber which may receive intake air via intakepassage 44 and may exhaust combustion gases via exhaust passage 48. Inone example, intake passage 44 may be configured as a ram-air intakewherein the dynamic pressure created by moving vehicle 102 may be usedto increase a static air pressure inside the engine's intake manifold.As such, this may allow a greater mass flow of air through the engine,thereby increasing engine power. Engine 10 as illustrated and describedherein may be included in a vehicle such as a road automobile, amongother types of vehicles. While the example applications of engine 10will be described with reference to a vehicle, it should be appreciatedthat various types of engines and vehicle propulsion systems may beused, including passenger cars, trucks, etc.

Cooling system 100 may circulate coolant through internal combustionengine 10 to absorb waste heat, and distributes the heated coolant toradiator 80 and/or heater core 55 via coolant lines 82 and 84,respectively. In one example, as depicted, cooling system 100 may becoupled to engine 10 and may circulate engine coolant from engine 10 toradiator 80 via engine-driven water pump 86, and back to engine 10 viacoolant line 82. Engine-driven water pump 86 may be coupled to theengine via front end accessory drive (FEAD) 36, and rotatedproportionally to engine speed via a belt, chain, etc. Specifically,engine-driven water pump 86 may circulate coolant through passages inthe engine block, head, etc., to absorb engine heat, which is thentransferred via the radiator 80 to ambient air. In one example, whereengine-driven water pump 86 is a centrifugal pump, the pressure (andresulting flow) produced by the pump may be proportional to thecrankshaft speed, or may be directly proportional to the engine speed.The temperature of the coolant may be regulated by a thermostat valve38, located in the cooling line 82, which may be kept closed until thecoolant reaches a threshold temperature.

Coolant may flow through coolant line 82, as described above, and/orthrough coolant line 84 to heater core 55 where the heat may betransferred to passenger compartment 104, and the coolant flows back toengine 10. In some examples, engine-driven pump 86 may operate tocirculate the coolant through both coolant lines 82 and 84.

One or more blowers and cooling fans may be included in cooling system100 to provide airflow assistance and augment a cooling airflow throughthe under-hood components. For example, cooling fan 91, coupled toradiator 80, may be operated when the vehicle is moving and the engineis running to provide cooling airflow assistance through radiator 80.Cooling fan 91 may draw a cooling airflow into under-hood compartment103 through an opening in the front-end of vehicle 102, for example,through grill 112. Such a cooling air flow may then be utilized byradiator 80 and other under-hood components (e.g., fuel systemcomponents, batteries, etc.) to keep the engine and/or transmissioncool. Further, the air flow may be used to reject heat from a vehicleair conditioning system. Further still, the airflow may be used toimprove the performance of a turbocharged/supercharged engine that isequipped with intercoolers that reduce the temperature of the air thatgoes into the intake manifold/engine. While this embodiment depicts onecooling fan, other examples may use multiple cooling fans.

Cooling fan 91 may be coupled to battery driven motor 93. During engineoperation, the engine generated torque may be transmitted to electricmachine 52 along a drive shaft, which may then be used by the electricmachine 52 to generate electrical power that may be stored in anelectrical energy storage device, such as battery 58. Battery 58 maythen be used to activate motor 93 via relays (not shown). Thus,operating the cooling fan system may include electrically poweringcooling fan rotation from engine rotational input, through thealternator and system battery, for example, when engine speed is below athreshold (for example, when the engine is in idle-stop). In otherembodiments, the cooling fan may be operated by enabling a variablespeed electric motor coupled to the cooling fan. In still otherembodiments, cooling fan 91 may be mechanically coupled to engine 10 viaa clutch (not shown) and operating the cooling fans may includemechanically powering their rotation from engine rotational output viathe clutch.

Under-hood compartment 103 may further include an air conditioning (AC)system comprising condenser 88, compressor 87, receiver drier 83,expansion valve 89, and evaporator 85 coupled to a blower (not shown).Compressor 87 may be coupled to engine 10 via FEAD 36 andelectromagnetic clutch 76 (also known as compressor clutch 76) whichallows the compressor to engage or disengage from the engine based onwhen the air conditioning system is turned on and switched off.Compressor 87 may pump pressurized refrigerant to condenser 88 mountedat the front of the vehicle. Condenser 88 may be cooled by cooling fans91 and 95, thereby, cooling the refrigerant as it flows through. Thehigh pressure refrigerant exiting condenser 88 may flow through receiverdrier 83 where any moisture in the refrigerant may be removed by the useof desiccants. Expansion valve 89 may then depressurize the refrigerantand allow it to expand before it enters evaporator 85 where it may bevaporized into gaseous form as passenger compartment 104 is cooled.Evaporator 85 may be coupled to a blower fan operated by a motor (notshown) which may be actuated by system voltage.

System voltage may also be used to operate an entertainment system(radio, speakers, etc.), electrical heaters, windshield wiper motors,rear window defrosting system and headlights amongst other systems.

FIG. 1 further shows a control system 14. Control system 14 may becommunicatively coupled to various components of engine 10 to carry outthe control routines and actions described herein. For example, as shownin FIG. 1, control system 14 may include an electronic digitalcontroller 12. Controller 12 may be a microcomputer, including amicroprocessor unit, input/output ports, an electronic storage mediumfor executable programs and calibration values, random access memory,keep alive memory, and a data bus. As depicted, controller 12 mayreceive input from a plurality of sensors 16, which may include userinputs and/or sensors (such as transmission gear position, gas pedalinput, brake input, transmission selector position, vehicle speed,engine speed, ambient temperature, intake air temperature, etc.),cooling system sensors (such as coolant temperature, fan speed,passenger compartment temperature, ambient humidity, etc.), and others(such as Hall Effect current sensors from the alternator and battery,system voltage regulator, etc.). Further, controller 12 may communicatewith various actuators 18, which may include engine actuators (such asfuel injectors, an electronically controlled intake air throttle plate,spark plugs, etc.), cooling system actuators (such as motor circuitrelays, etc.), and others. The controller 12 employs the variousactuators of FIG. 1 to adjust engine operation based on the receivedsignals and instructions stored on a memory of the controller. In someexamples, the storage medium may be programmed with computer readabledata representing instructions executable by the processor forperforming the methods described below as well as other variants thatare anticipated but not specifically listed.

Engine controller 12 may adjust the operation of cooling fan 91 tocontrol air flow through radiator 80 based on vehicle cooling demands,vehicle operating conditions, and in coordination with engine operationby actuating motor 93. In one example, during a first vehicle movingcondition, when the engine is operating, and vehicle cooling and airflowassistance from the fan is desired, cooling fan 91 may be powered byenabling battery-driven electric motor 93 to provide airflow assistancein cooling under-hood components. The first vehicle moving condition mayinclude, for example, when an engine temperature is above a threshold.In another example, during a second vehicle moving condition, whenairflow assistance is not desired (for example, due to sufficientvehicle motion-generated airflow through the under-hood compartment),fan operation may be discontinued by disabling the fan motor. In anotherexample, during a third vehicle moving condition when an air conditioneris operational, cooling fan 91 may be activated to enable cooling of airconditioner condenser 88.

In some examples, vehicle 102 may be a hybrid vehicle with multiplesources of torque available to one or more vehicle wheels 106. In otherexamples, vehicle 102 is a conventional vehicle with only an engine, oran electric vehicle with only electric machine(s). In the example shown,vehicle 102 includes engine 10 and an electric machine 52. Electricmachine 52 may be a motor or a motor/generator. Crankshaft 140 of engine10 and electric machine 52 are connected via a transmission 54 tovehicle wheels 106 when one or more clutches 56 are engaged. In thedepicted example, a first clutch 56 is provided between crankshaft 140and electric machine 52, and a second clutch 56 is provided betweenelectric machine 52 and transmission 54. Controller 12 may send a signalto an actuator of each clutch 56 to engage or disengage the clutch, soas to connect or disconnect crankshaft 140 from electric machine 52 andthe components connected thereto, and/or connect or disconnect electricmachine 52 from transmission 54 and the components connected thereto.Transmission 54 may be a gearbox, a planetary gear system, or anothertype of transmission. The powertrain may be configured in variousmanners including as a parallel, a series, or a series-parallel hybridvehicle.

Electric machine 52 receives electrical power from battery 58 to providetorque to vehicle wheels 106. Electric machine 52 may also be operatedas a generator to provide electrical power to charge battery 58, forexample during a braking operation.

FIG. 2 shows flow chart of an example method 200 for determining bladearrangement of a fan. In one example, the spacing between adjacentblades may be selected from one of the small, medium, and largespacings. The size of the small, medium, and large spacings, as well asthe sequence of arrangement of these spacings circumferentially aroundthe fan hub may be determined through an optimization process. In theoptimization process, the imbalance force and the pressure at selectedfrequencies generated by the rotating fan are minimized to reduce theNVH caused by the first order imbalance force and high order harmonicnoises.

At 202, the number of fan blades n is determined. As an example, thenumber of blade may be determined by parameters including radiatordimension, desired air flow rate, and desired air flow volume.

At 204, boundary conditions are determined. The boundary conditions mayinclude the range of the blade spacings. For example, the spacingbetween two adjacent blades ΔB_(i) may be selected from three rangesincluding the small blade spacing S, the medium blade spacing M, and thelarge blade spacing L:

$\begin{matrix}{{{\Delta \; B_{i}} \in \left\{ {S,M,L} \right\}},{i \in \left\{ {1\mspace{14mu} \ldots \mspace{14mu} n} \right\}},{{\frac{360}{n} - {\alpha \frac{\delta}{2}}} < M < {\frac{360}{n} + {\alpha \frac{\delta}{2}}}},{\alpha \in \left( {0,1} \right\rbrack},{{\frac{360}{n} - \delta} \leq S \leq {\frac{360}{n} - \frac{\delta}{2}}},{{\frac{360}{n} + \frac{\delta}{2}} \leq L \leq {\frac{360}{n} + \delta}},{\delta \in \left( {0,10} \right\rbrack},} & {{Condition}\mspace{14mu} 1}\end{matrix}$

wherein Δ is a deviation angle from a nominal value

$\frac{360}{n}.$

The range of me deviation δ may be determined based on the fanperformance and the durability of the rotor. The coefficient α isdetermined based on the pattern of the optimal designs, and variesresponsive to the number of blades. As an example, for each fan, thesize of blading spacing within the same range (i.e., within the samesmall, medium, or large blade spacing) does not have to be exactly thesame but should meet Condition 1. As another example, the size ofblading spacing in the same range is the same.

The boundary conditions may further include that the total spacings ofthe fan is 360 degrees:

Σ_(i=1) ^(n) ΔB _(i)=360.   Condition 2

At 206, a screening DOE (design of experiments) table is initiated toexplore the full design space. The screening DOE table may include theblade arrangement. The blade arrangement may include the size andsequence of blade spacing between each adjacent blades around the hub.The screening DOE table may also include the imbalance force and themagnitude of pressure at selected frequencies for the blade arrangement.In one example, the frequencies may be selected to be objectionable fantonal frequencies. The frequencies may be selected based on thefrequency range of human ear sensitivity and the frequency range of theengine noise. For example, the frequencies may be selected to be lowerthan the frequency of engine noise and within the range of human earsensitivity. In one embodiment, the selected frequencies may include thethird harmonic frequency. In another embodiment, the selectedfrequencies may include each and every of the third harmonic frequency,the fourth harmonic frequency, and the fifth harmonic frequency.

In one embodiment, method 200 may initiate the screening DOE table bysetting the size of blade spacing between each adjacent blades to be

$\frac{360}{n}.$

Further, method 200 may set the imbalance force and the pressure atselected frequencies to a large number.

At 208, the pressure and the imbalance force for a most recentlygenerated blade arrangement are calculated. The blade arrangement may bethe initiated blade arrangement at 206, responsive to the initiation ofthe screening DOE table. The blade arrangement may alternatively be anewly generated blade arrangement in a design optimization table.

In one embodiment, when calculating the pressure and the imbalanceforce, it may be assumed that all blades are identical in size, shape,and pitch; and each blade generates the same centrifugal force when thefan rotates. Further, it may be assumed that each blade generates thesame triangular pressure pulse. The air pressure generated by rotatingthe fan may be calculated by taking Fourier transformation of thepressure pulses. The imbalance force may be calculated as a function ofthe rotation speed of the fan, the blade arrangement, and the mass ofthe blade. In one example, the imbalance force may be the sum of forcegenerated by each blade in one revolution.

At 210, method 200 calculates a cost function based on the imbalanceforce and magnitude of pressure generated by the rotating fan at thefrequencies determined at 206. As one example, magnitude of pressure atthe selected frequencies determined at 206 are identified. In oneembodiment, the cost function may be constructed as a weighted sum ofthe pressure magnitudes at the selected frequencies, as well as theimbalance force calculated at 206. For example, the pressure magnitudeat each selected frequencies may be assigned with a first weightingfactor, and the imbalance force may be assigned with a second weightingfactor. The cost function may be the sum of the pressure magnitudesmultiplied with the first weighting factor and the imbalance forcemultiplied with the second weighting factor. In another embodiment, thepressure magnitude at each selected frequencies may be assigned withdifferent weighting factors. The weighting factors may be determinedbased on the sensitivity of the human ear at the particular frequency.The calculated cost function, pressure magnitude at the selectedfrequencies, and imbalance force may be saved in the screening DOEtable.

At 212, the method determines if the most recently generated bladearrangement is the optimal arrangement. In one example, method 200 maydetermine that the arrangement is optimal if 1) the difference betweenthe recently generated arrangement and the previous arrangement is lessthan a threshold; and 2) the cost function calculated at 210 is lessthan a threshold. In other words, method 200 may stop the optimizationprocess if a local minimum has been reached. If the optimal bladearrangement is found, method moves to 216 to output the optimal bladearrangement. Otherwise, method 200 moves to 214.

At 214, the design optimization table is generated based on the DOEexploration In one example, generating the design optimization table mayinclude generating a new blade arrangement, or the size and sequence ofblade spacings between adjacent blades around the hub, is bounded byCondition 1 and Condition 2 defined at 204. The new blade arrangementmay be generated via genetic algorithm of multi-objective optimization.After the new blade arrangement is generated, method 200 moves on to 208to calculate the pressure and imbalance force of the newly generatedblade arrangement.

FIG. 3 shows example results of the optimization process for a six-bladefan. Each grey-scaled dot on the graph indicates a blade arrangementwithin the DOE table. For each blade arrangement, the imbalance force,the pressure magnitude at the third harmonic, the fourth harmonic, andthe fifth harmonic frequencies are illustrated. Reduced imbalance forceand reduced pressure magnitude result in reduced NVH. The x-axisindicates the imbalance force, and arrow 302 indicates reduced NVH. They-axis indicates pressure magnitude at the third harmonic frequency, andarrow 301 indicates reduced NVH. The pressure magnitude at the fourthharmonic is indicated by the grey scales. The pressure magnitude at thefifth harmonic is indicated by the size of the dot. Withoutoptimization, the blade arrangement 303 of the fan with non-optimizedspacings can generated high NVH at the fundamental, the third harmonic,the fourth harmonic, and the fifth harmonic frequencies. Throughoptimization, NVH of blade arrangement 304 of the fan may be reduced bydecreased imbalance force, and decreased pressure magnitude across theselected frequencies, especially in the third harmonic frequency.

FIGS. 4A-4B, 5A-5B, 6A-6B, and 7A-7B show optimized arrangements ofblade spacings for a fan with six, seven, eight, and nine blades. Eachfan includes a hub at the center. The blades are arrangedcircumferentially around the hub. The fan may be rotated around thecentral axis of the hub to increase air flow. The blades are identical,and are coupled to the hub in the same way. For example, the blades havethe same size, shape, and pitch. Each blade includes a leading edgeindicated by the dashed lines. Each two of adjacent blades are separatedby a spacing. For example, in FIG. 4A, adjacent blades 411 and 412 areseparated by spacing 440. In one embodiment, the spacing betweenadjacent blades may be defined by the radial angle between the adjacentleading edges. For example, in FIG. 4A, the spacing between adjacentblades 411 and 412 is the radial angle 440 of between the leading edge430 of blade 411 and the leading edge 431 of blade 412. Blade 411 andblade 412 are arranged adjacent to each other, with no other blade inbetween. In another embodiment, the spacing may be defined by the radialangle between the central axes of the blades. The spacing may beselected from one of the small blade spacing S, the medium blade spacingM, and the large blade spacing L. The range of each blade spacing isdefined in Condition 1 at step 204 of FIG. 2. As such, circumferentiallyand clockwise around the hub, the blade spacings may be arranged in acombination or sequence of the small blade spacing, the medium bladespacing, and the large blade spacing. For example, in FIG. 4A, thesequence of blade spacing of the fan is MLSSM without any other spacingstherebetween L, which corresponds to spacings in the sequence of 440,441, 442, 443, 444, 445.

FIGS. 4A-4B show two examples of six-blade fan with spacings selectedfrom the small blade spacing, the medium blade spacing, and the largeblade spacing. The small blade spacing S is in the range of

${{\frac{360}{6} - \delta} \leq S \leq {\frac{360}{6} + \frac{\delta}{2}}},$

the medium spacing M is in the range of

${{\frac{360}{6} - \frac{\delta}{2}} < M < {\frac{360}{6} + \frac{\delta}{2}}},$

and the large spacing L is in the range of

${{\frac{360}{6} + \frac{\delta}{2}} \leq L \leq {\frac{360}{6} + \delta}},$

wherein δ ∈ (0,10]. Both examples include two small blade spacings, twomedium blade spacings, and two large blade spacings, wherein the mediumblade spacing is smaller than the large blade spacing and larger thanthe small blade spacing.

In FIG. 4A, blades 411, 412, 413, 414, 415, and 416 are arrangedcircumferentially around hub 410. Blades 411 are 412 are separated byspacing 440. Blades 412 and 413 are separated by spacing 441. Blades 413and 414 are separated by spacing 442. Blades 414 and 415 are separatedby spacing 443. Blades 415 and 416 are separated by spacing 444. Blades416 and 411 are separated by spacing 445. Spacings 442 and 443 are smallblade spacing S, and are adjacent to each other. Spacings 440 and 444are medium spacings M. Spacings 445 and 441 are large spacings L. Assuch, the small blade spacing, the medium blade spacing, and the largeblade spacing are arranged in a sequence of MLSSML circumferentiallyaround the hub without any other spacings therebetween. In one example,the size of the blade spacing between adjacent blades around the hub are56.5°, 68.6°, 50°, 54.9°, 60°, and 70°.

In FIG. 4B, blades 421, 422, 423, 424, 425, and 426 are arrangedcircumferentially around hub 420. Blades 421 are 422 are separated byspacing 451. Blades 422 and 423 are separated by spacing 452. Blades 423and 424 are separated by spacing 453. Blades 424 and 425 are separatedby spacing 454. Blades 425 and 426 are separated by spacing 456. Blades426 and 421 are separated by spacing 456. Spacings 456 and 453 are smallspacing S. Spacings 451 and 454 are medium spacing M. Spacings 452 and455 are large spacing L. As such, the small blade spacing, the mediumblade spacing, and the large blade spacing are arranged in a sequence ofMLSMLS circumferentially around the hub 420. The two small bladespacings are opposite to each other relative to the hub 420. The twomedium blade spacings are opposite to each other relative to the hub420. The two large blade spacings are opposite to each other relative tothe hub 420.

FIGS. 5A-5B show two examples of seven-blade fan with spacings selectedfrom the small blade spacing, the medium blade spacing, and the largeblade spacing. The spacings include one medium blade spacing, at leasttwo small blade spacings adjacent to each other, and at least two largeblade spacings. The small blade spacing S is in the range of

${{\frac{360}{7} - \delta} \leq S \leq {\frac{360}{7} + \frac{\delta}{2}}},$

the medium spacing M is in the range of

${{\frac{360}{7} - \frac{\delta}{2}} < M < {\frac{360}{7} + \frac{\delta}{2}}},$

and the large spacing L is in the range of

${{\frac{360}{7} + \frac{\delta}{2}} \leq L \leq {\frac{360}{7} + \delta}},$

wherein δ ∈ (0,10].

In FIG. 5A, blades 511, 512, 513, 514, 515, 516, and 517 are arrangedcircumferentially around hub 510. Blades 511 are 512 are separated byspacing 531. Blades 512 and 513 are separated by spacing 532. Blades 513and 514 are separated by spacing 533. Blades 514 and 515 are separatedby spacing 534. Blades 515 and 516 are separated by spacing 535. Blades516 and 517 are separated by spacing 536. Blade 517 and 511 areseparated by spacing 537. Spacings 531, 532, and 535 are small spacingS. Spacings 534 is medium spacing M. Spacings 533, 536, and 537 arelarge spacing L. As such, the small blade spacing, the medium bladespacing, and the large blade spacing are arranged in a sequence ofSSLMSLL circumferentially around the hub without any other spacingstherebetween. In one example, the size of the blade spacing betweenadjacent blades around the hub are 42.3°, 44.1°, 58.8°, 55.6°, 41.4°,56.4°, and 61.4°.

In FIG. 5B, blades 521, 522, 523, 524, 525, 526, and 527 are arrangedcircumferentially around hub 520. Blades 521 are 522 are separated byspacing 541. Blades 522 and 523 are separated by spacing 542. Blades 523and 524 are separated by spacing 543. Blades 524 and 525 are separatedby spacing 544. Blades 525 and 526 are separated by spacing 545. Blades526 and 527 are separated by spacing 546. Blade 527 and 521 areseparated by spacing 547. Spacings 541, 542, 545, and 546 are smallspacing S. Spacings 544 is medium spacing M. Spacings 543, and 547 arelarge spacing L. As such, the small blade spacing, the medium bladespacing, and the large blade spacing are arranged in a sequence ofSSLMSSL circumferentially around the hub without any other spacingstherebetween.

FIGS. 6A-6B shows two examples of eight-blade fan with spacing selectedfrom the small blade spacing, the medium blade spacing, and the largeblade spacing. The small blade spacing S is in the range of

${{\frac{360}{8} - \delta} \leq S \leq {\frac{360}{8} + \frac{\delta}{2}}},$

the medium blade spacing M is in the range of

${{\frac{360}{8} - {0.8\frac{\delta_{\min}}{2}}} < M < {\frac{360}{7} + {0.8\frac{\delta_{\max}}{2}}}},$

and the large spacing L is in the range of

${{\frac{360}{8} + \frac{\delta}{2}} \leq L \leq {\frac{360}{8} + \delta}},{\delta \in {\left( {0,10} \right\rbrack.}}$

The spacings include a plurality of small blade spacings S and aplurality of large blade spacings L arranged in the sequence of LLSSLcircumferentially around the hub without any other spacingstherebetween.

In FIG. 6A, blades 611, 612, 613, 614, 615, 616, 617, and 618 arearranged circumferentially around hub 610. Blades 611 are 612 areseparated by spacing 631. Blades 612 and 613 are separated by spacing632. Blades 613 and 614 are separated by spacing 633. Blades 614 and 615are separated by spacing 634. Blades 615 and 616 are separated byspacing 635. Blades 616 and 617 are separated by spacing 636. Blade 617and 618 are separated by spacing 637. Blade 618 and 611 are separated byspacing 638. Spacings 631, 635, and 636 are small spacing S. Spacings632 and 638 are medium spacing M. Spacings 633, 634, and 637 are largespacing L. As such, the small blade spacing, the medium blade spacing,and the large blade spacing are arranged in a sequence of SMLLSSLMcircumferentially around the hub without any other spacingstherebetween. In one example, the size of the blade spacing betweenadjacent blades around the hub are 35°, 43.6°, 50°, 55°, 37.7°, 35°,55°, and 48.7°.

In FIG. 6B, blades 621, 622, 623, 624, 625, 626, 627, and 628 arearranged circumferentially around hub 620. Blades 621 are 622 areseparated by spacing 641. Blades 622 and 623 are separated by spacing642. Blades 623 and 624 are separated by spacing 643. Blades 624 and 625are separated by spacing 644. Blades 625 and 626 are separated byspacing 645. Blades 626 and 627 are separated by spacing 646. Blade 627and 628 are separated by spacing 647. Blade 628 and blade 621 areseparated by spacing 648. Spacings 642, 643, 646, and 647 are smallspacing S. Spacings 641, 644, 645, and 648 are large spacing L. As such,the small blade spacing and the large blade spacing are arranged in asequence of LSSLLSSL circumferentially around the hub without any otherspacings therebetween.

FIGS. 7A-7C show three examples of nine-blade fan with spacing selectedfrom the small blade spacing, the medium blade spacing, and the largeblade spacing. The small blade spacing S is in the range of

${{\frac{360}{9} - \delta} \leq S \leq {\frac{360}{9} + \frac{\delta}{2}}},$

the medium blade spacing M is in the range of

${{\frac{360}{9} - {0.2\frac{\delta}{2}}} < M < {\frac{360}{9} + {0.2\frac{\delta}{2}}}},$

and the large spacing L is in the range of

${{\frac{360}{9} + \frac{\delta}{2}} \leq L \leq {\frac{360}{9} + \delta}},{\delta \in {\left( {0,10} \right\rbrack.}}$

In one example, the optimized spacings include a plurality of smallblade spacings S and a plurality of large blade spacings L arranged in asequence of LLSS circumferentially around the hub without any otherspacings therebetween. In another example, the optimized spacing includeone medium spacing.

In an example fan of FIG. 7A, blades 711-719 are arrangedcircumferentially clockwise around hub 710. The adjacent blades areseparated by spacings 741-749. Spacings 741, 742, 743, 746, and 747 aresmall spacings S. Spacing 715 is medium spacing M. Spacings 744, 748,and 749 are large spacing L. As such, the small blade spacing, themedium blade spacing, and the large blade spacing are arranged in asequence of SSSLMSSLL clockwise around the hub without any otherspacings therebetween. In one example, the size of the blade spacingbetween adjacent blades around the hub are 35°, 35°, 35°, 50°, 40°, 35°,35°, 45°, and 50°.

In an example fan of FIG. 7B, blades 721-729 are arrangedcircumferentially clockwise around hub 720. The adjacent blades areseparated by spacings 751-759. Spacings 753, 754, 758, and 759 are smallspacings S. Spacing 755 is medium spacing M. Spacings 751, 752, 756, and757 are large spacing L. As such, the small blade spacing, the mediumblade spacing, and the large blade spacing are arranged in a sequence ofLLSSMLLSS clockwise around the hub without any other spacingstherebetween.

In an example fan of FIG. 7C, blades 731-739 are arrangedcircumferentially clockwise around hub 730. The adjacent blades areseparated by spacings 761-769. Spacings 762, 763, 767, and 768 are smallspacings S. Spacing 765 is medium spacing M. Spacings 761, 764, 766, and769 are large spacing L. As such, the small blade spacing, the mediumblade spacing, and the large blade spacing are arranged in a sequence ofLSSLMLSSL clockwise around the hub without any other spacingstherebetween.

In this way, by optimizing the spacing of blades of a fan, the NVHgenerated by the fan due to imbalance force as well as pressuregenerated at selected harmonics may be reduced. The technical effect ofminimizing the pressure magnitude at selected harmonics is that noisesthat cannot covered by engine noise may be reduced. The technical effectof minimizing the imbalance force is that NVH due to asymmetricarrangement of blade spacing may be reduced. The technical effect ofselecting the spacing between adjacent blades from the small, medium,and large spacing is that the process of assembling the fan may besimplified.

As one embodiment, a fan comprises a hub; and six blades disposedcircumferentially around the hub with uneven spacings between adjacentblades, the spacings include two small blade spacings, two medium bladespacings, and two large blade spacings, wherein the medium blade spacingsmaller than the large blade spacing and larger than the small bladespacing. In a first example of the fan, the small blade spacing S is ina range of

${{\frac{360}{6} - \delta} \leq S \leq {\frac{360}{6} + \frac{\delta}{2}}},$

the medium spacing M is in a range of

${{\frac{360}{6} - \frac{\delta}{2}} < M < {\frac{360}{6} + \frac{\delta}{2}}},$

and the large spacing L is in a range of

${{\frac{360}{6} + \frac{\delta}{2}} \leq L \leq {\frac{360}{6} + \delta}},$

wherein δ ∈ (0,10]. A second example of the fan optionally includes thefirst example and further includes wherein the two small blade spacingsare adjacent to each other. A third example of the fan optionallyincludes one or more of the first and second examples, and furtherincludes wherein the small blade spacing S, the medium blade spacing M,and the large blade spacing L are arranged in a sequence of MLSSMLcircumferentially around the hub without any other spacingstherebetween. A fourth example of the fan optionally includes one ormore of the first through third examples, and further includes, where inthe two small blade spacings are opposite to each other relative to thehub, the two medium blade spacings are opposite to each other relativeto the hub, and the two large blade spacings are opposite to each otherrelative to the hub. A fifth example of the fan optionally includes oneor more of the first through fourth examples, and further includes,wherein the small blade spacing, the medium blade spacing, and the largeblade spacing are arranged in a sequence of MLSMLS circumferentiallyaround the hub without any other spacings therebetween.

As another embodiment, a fan comprises a hub; and seven blades disposedcircumferentially around the hub with uneven spacings between adjacentblades, wherein the spacings include one medium blade spacing, at leasttwo small blade spacings adjacent to each other, and at least two largeblade spacings. In a first example of the fan, the small blade spacing Sis in a range of

${{\frac{360}{7} - \delta} \leq S \leq {\frac{360}{7} + \frac{\delta}{2}}},$

the medium spacing M is in a range of

${{\frac{360}{7} - \frac{\delta}{2}} < M < {\frac{360}{7} + \frac{\delta}{2}}},$

and the large spacing L is in a range of

${{\frac{360}{7} + \frac{\delta}{2}} \leq L \leq {\frac{360}{7} + \delta}},$

wherein δ ∈ (0,10]. A second example of the fan optionally includes thefirst example and further includes, wherein the small blade spacing S,the medium blade spacing M, and the large blade spacing L are arrangedin a sequence of SSLMSLL circumferentially around the hub without anyother spacings therebetween. A third example of the fan optionallyincludes one or more of the first and second examples, and furtherincludes, wherein the small blade spacing, the medium blade spacing, andthe large blade spacing are arranged in a sequence of SSLMSSLcircumferentially around the hub without any other spacingstherebetween.

As another embodiment, a fan comprises a hub; and eight blades disposedcircumferentially around the hub with uneven spacings between adjacentblades, wherein the spacings include a plurality of small blade spacingsS and a plurality of large blade spacings L arranged in the sequence ofLLSSL circumferentially around the hub without any other spacingstherebetween. In a first example of the fan, the small blade spacing Sis in a range of

${{\frac{360}{8} - \delta} \leq S \leq {\frac{360}{8} + \frac{\delta}{2}}},$

and the large spacing L is in a range of

${{\frac{360}{8} + \frac{\delta}{2}} \leq L \leq {\frac{360}{8} + \delta}},$

wherein δ ∈ (0,10]. A second example of the fan optionally includes thefirst example and further includes, a medium blade spacing, the mediumblade spacing smaller than the large blade spacing and larger than thesmall blade spacing, the medium spacing M is in a range of

${\frac{360}{8} - {0.8\frac{\delta}{2}}} < M < {\frac{360}{7} + {0.8{\frac{\delta}{2}.}}}$

A third example of the fan optionally includes one or more of the firstand second examples, and further includes, wherein the small bladespacing, the medium blade spacing, and the large blade spacing arearranged in a sequence of SMLLSSLM circumferentially around the hubwithout any other spacings therebetween. A fourth example of the fanoptionally includes one or more of the first through third examples, andfurther includes, wherein the small blade spacing, the medium bladespacing, and the large blade spacing are arranged in a sequence ofLSSLLSSL circumferentially around the hub without any other spacingstherebetween.

As another embodiment, a fan comprises a hub; and nine blades disposedcircumferentially around the hub with uneven spacings between adjacentblades, wherein the spacings include a plurality of small blade spacingsS and a plurality of large blade spacings L arranged in a sequence ofLLSS circumferentially around the hub. In a first example of the fan,the fan further include one medium spacing M, the medium blade spacingsmaller than the large blade spacing and larger than the small bladespacing, the medium spacing is in a range of

${{\frac{360}{9}0.2\frac{\delta}{2}} < M < {\frac{360}{9} + {0.2\frac{\delta}{2}}}},$

wherein δ ∈ (0,10] . A second example of the fan optionally includes thefirst example and further includes, wherein the small blade spacing, themedium blade spacing, and the large blade spacing are arranged in asequence of SSSLMSSLL circumferentially around the hub without any otherspacings therebetween. A third example of the fan optionally includesone or more of the first and second examples, and further includes,wherein the small blade spacing, the medium blade spacing, and the largeblade spacing are arranged in a sequence of LLSSMLLSS circumferentiallyaround the hub without any other spacings therebetween. A fourth exampleof the fan optionally includes one or more of the first through thirdexamples, and further includes, wherein the small blade spacing, themedium blade spacing, and the large blade spacing are arranged in asequence of LSSLMLSSL circumferentially around the hub without any otherspacings therebetween.

In another representation, the fan may be a cooling fan installed in ahybrid vehicle.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A fan, comprising: a hub; and six blades disposed circumferentiallyaround the hub with uneven spacings between adjacent blades, thespacings include two small blade spacings, two medium blade spacings,and two large blade spacings, wherein the medium blade spacing issmaller than the large blade spacing and larger than the small bladespacing.
 2. The fan of claim 1, wherein the small blade spacing S is ina range of${{\frac{360}{6} - \delta} \leq S \leq {\frac{360}{6} + \frac{\delta}{2}}},$the medium spacing M is in a range of${{\frac{360}{6} - \frac{\delta}{2}} < M < {\frac{360}{6} + \frac{\delta}{2}}},$and the large spacing L is in a range of${{\frac{360}{6} + \frac{\delta}{2}} \leq L \leq {\frac{360}{6} + \delta}},$wherein δ ∈(0,10].
 3. The fan of claim 1, wherein the two small bladespacings are adjacent to each other.
 4. The fan of claim 3, wherein thesmall blade spacing S, the medium blade spacing M, and the large bladespacing L are arranged in a sequence of MLSSML circumferentially aroundthe hub without any other spacings therebetween.
 5. The fan of claim 1,wherein the two small blade spacings are opposite to each other relativeto the hub, the two medium blade spacings are opposite to each otherrelative to the hub, and the two large blade spacings are opposite toeach other relative to the hub.
 6. The fan of claim 5, wherein the smallblade spacing, the medium blade spacing, and the large blade spacing arearranged in a sequence of MLSMLS circumferentially around the hubwithout any other spacings therebetween.
 7. A fan, comprising: a hub;and seven blades disposed circumferentially around the hub with unevenspacings between adjacent blades, wherein the spacings include onemedium blade spacing, at least two small blade spacings adjacent to eachother, and at least two large blade spacings.
 8. The fan of claim 7,wherein the small blade spacing S is in a range of${{\frac{360}{7} - \delta} \leq S \leq {\frac{360}{7} + \frac{\delta}{2}}},$the medium spacing M is in a range of${{\frac{360}{7} - \frac{\delta}{2}} < M < {\frac{360}{7} + \frac{\delta}{2}}},$and the large spacing L is in a range of${{\frac{360}{7} + \frac{\delta}{2}} \leq L \leq {\frac{360}{7} + \delta}},$wherein δ ∈ (0,10].
 9. The fan of claim 7, wherein the small bladespacing S, the medium blade spacing M, and the large blade spacing L arearranged in a sequence of SSLMSLL circumferentially around the hubwithout any other spacings therebetween.
 10. The fan of claim 7, whereinthe small blade spacing, the medium blade spacing, and the large bladespacing are arranged in a sequence of SSLMSSL circumferentially aroundthe hub without any other spacings therebetween.
 11. A fan, comprising:a hub; and eight blades disposed circumferentially around the hub withuneven spacings between adjacent blades, wherein the spacings include aplurality of small blade spacings S and a plurality of large bladespacings L arranged in the sequence of LLSSL circumferentially aroundthe hub without any other spacings therebetween.
 12. The fan of claim11, wherein the small blade spacing S is in a range of${{\frac{360}{8} - \delta} \leq S \leq {\frac{360}{8} + \frac{\delta}{2}}},$and the large spacing L is in a range of${{\frac{360}{8} + \frac{\delta}{2}} \leq L \leq {\frac{360}{8} + \delta}},$wherein δ ∈ (0,10].
 13. The fan of claim 12, further includes a mediumblade spacing, the medium blade spacing smaller than the large bladespacing and larger than the small blade spacing, the medium spacing M isin a range of${\frac{360}{8} - {0.8\frac{\delta}{2}}} < M < {\frac{360}{7} + {0.8{\frac{\delta}{2}.}}}$14. The fan of claim 13, wherein the small blade spacing, the mediumblade spacing, and the large blade spacing are arranged in a sequence ofSMLLSSLM circumferentially around the hub without any other spacingstherebetween.
 15. The fan of claim 11, wherein the small blade spacing,the medium blade spacing, and the large blade spacing are arranged in asequence of LSSLLSSL circumferentially around the hub without any otherspacings therebetween.
 16. A fan, comprising: a hub; and nine bladesdisposed circumferentially around the hub with uneven spacings betweenadjacent blades, wherein the spacings include a plurality of small bladespacings S and a plurality of large blade spacings L arranged in asequence of LLSS circumferentially around the hub without any otherspacings therebetween.
 17. The fan of claim 16, further include onemedium spacing M, the medium blade spacing smaller than the large bladespacing and larger than the small blade spacing, the medium spacing isin a range of${{\frac{360}{9} - {0.2\frac{\delta}{2}}} < M < {\frac{360}{9} + {0.2\frac{\delta}{2}}}},$wherein δ ∈ (0,10].
 18. The fan of claim 16, wherein the small bladespacing, the medium blade spacing, and the large blade spacing arearranged in a sequence of SSSLMSSLL circumferentially around the hubwithout any other spacings therebetween.
 19. The fan of claim 16,wherein the small blade spacing, the medium blade spacing, and the largeblade spacing are arranged in a sequence of LLSSMLLSS circumferentiallyaround the hub without any other spacings therebetween.
 20. The fan ofclaim 16, wherein the small blade spacing, the medium blade spacing, andthe large blade spacing are arranged in a sequence of LSSLMLSSLcircumferentially around the hub without any other spacingstherebetween.